Difference between revisions of "Real Time Clock"
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In the picture to the right you can see a [[DS1307]] chip driven by the 32,768 KHz X-tal. The reason for chosing 32768 Hz is that 2<sup>15</sup> = 32768. The DS1307 contains a counter that repeatedly counts to 2<sup>15</sup>. Each time the counter reaches 32768 the time clock counts one second forward. Battery power backup is provided by the battery just visible in top right corner. | In the picture to the right you can see a [[DS1307]] chip driven by the 32,768 KHz X-tal. The reason for chosing 32768 Hz is that 2<sup>15</sup> = 32768. The DS1307 contains a counter that repeatedly counts to 2<sup>15</sup>. Each time the counter reaches 32768 the time clock counts one second forward. Battery power backup is provided by the battery just visible in top right corner. | ||
| − | Beside the RTC the DS1307 contains 112 Bytes of [[RAM]] often used for configuration and password information. The time and contents of RAM are lost if the chip losses power. | + | Beside the RTC the DS1307 contains 112 Bytes of [[RAM]] often used for configuration and password information. The time and contents of RAM are lost if the chip losses power. |
| + | =Motorola MC146818= | ||
| + | The most used RTC design was the Motorola [[MC146818]] chip introduced in the PC/AT in 1984<ref>[http://www.ust.hk/itsc/y2k/y2k_pc_rtclock.html Use of MC146818 in PC's]</ref>. Today the RTC in is an integrated part of the PC mainboard chipset, but still emulating the MC146818. | ||
=References= | =References= | ||
<references/> | <references/> | ||
[[Category:RTC]] | [[Category:RTC]] | ||
Revision as of 11:17, 10 July 2013
A RTC or Real Time Clock is a build in time clock in electronic equipment such as an PC or an embedded processor. The RTC often has a battery power backup and the time are retained using a precision X-tal to minimize drift of time.
DS1307 RTC chip
A popular stand alone RTC chip is the DS1307 used by example by the popular Arduino[1] embedded system.
In the picture to the right you can see a DS1307 chip driven by the 32,768 KHz X-tal. The reason for chosing 32768 Hz is that 215 = 32768. The DS1307 contains a counter that repeatedly counts to 215. Each time the counter reaches 32768 the time clock counts one second forward. Battery power backup is provided by the battery just visible in top right corner.
Beside the RTC the DS1307 contains 112 Bytes of RAM often used for configuration and password information. The time and contents of RAM are lost if the chip losses power.
Motorola MC146818
The most used RTC design was the Motorola MC146818 chip introduced in the PC/AT in 1984[2]. Today the RTC in is an integrated part of the PC mainboard chipset, but still emulating the MC146818.